Growing "Up"

Tomorrow is my 21st birthday, and I feel strangely contemplative about it. 21 is considered by most to be the threshold into adulthood, the age that springboards us from adolescence to maturity, where we put away childish things and live as men and women. But in this day and age, that doesn't quite seem to be the case anymore. As people continue to live longer and longer, the date by which we're expected to "mature" seems to get pushed farther and farther back as well. There are people in their 30's, hell even their 40's or 50's, who party like they're teenagers or twenty-somethings. Are they not past the age to "mature" and give up such past-times, even after having birthed children and become parents? Or are we really ever expected to "mature"? As long as we fulfill our financial obligations, does that mean that we're free to forever more act like adolescents? Even know it seems the world is plagued by the "man-child" and the "woman-child",in reality, is that really such a bad thing? Isn't staying young at heart what keeps us from becoming bitter and cynical and helps us live longer, happier lives? But then again, isn't having drunken wild nights way past your prime incurring upon what time you have left as well? A catch-22, I believe.